الفهرس 
Theoretical Background and Literature ReviewOnly 14 pages are availabe for public view
 |  | from | 226 |  |  |
| | | from | 226 | | |
Abstract
This thesis represents a theoretical and experimental study for
physical properties of some organic compounds. This thesis consists of
four chapters, conclusion and list of references.
The thesis begins with a short theoretical background about the
field of computational physics, starting from the basic many-body
problems to the Hartree-Fock (HF) and density functional theory
(DFT). The Gaussian 03W and Gauss view (4.1) program package,
basis sets, origin of molecular vibrations and IR spectroscopy. We also
represent the theory of light absorption, UV/Vis spectroscopy, theory of
charge transport process in organic semiconductors and finally the
theory of organic photovoltaic solar cell.
Then it represented a brief overview of the experimental
techniques used in this thesis. It describes the basic of the conventional
thermal evaporation (vacuum deposition) techniques, the configuration
of the sample preparation, the film thickness measurement methods, the
techniques that used to determine the molecular structure, i.e. proton
nuclear magnetic resonance (1H-NMR) measurements, single crystal Xray
stereo-diffractometer, X-ray diffraction pattern (XRD) and Fourier
transform infrared spectroscopy (FT-IR) techniques, the techniques that
used to determine the optical properties usually the spectrophotometric
measurement of transmittance (T) and reflectance (R) at normal
incidence of light and also the techniques that used to determine the
electrical properties.
The results of a computational study for the molecular structure of
2-(2-furanylmethylene) propanedinitrile (FMN) and its electrical properties are also represented. The equilibrium geometries, harmonic
vibrational frequencies, thermo-chemical parameters, total dipole
moment and HOMO-LUMO energies are calculated by HF utilizing 6-
31G and 6-311G basis sets and DFT/B3LYP utilizing 6-31G and 6-
31lG basis sets. Comparison of the vibrational frequencies calculated at
B3LYP utilizing 6-31G and 6-311G basis sets with experimental values
reveals that B3LYP/6-311G gives reasonable deviations from the
experimental values. The results showed that 2-(2-furanylmethylene)
propanedinitrile possesses a dipole moment of 7.5 Debye and HOMOLUMO
energy gap of 3.92 eV. The electrical properties of 2-(2-
furanylmethylene) propanedinitrile thin film is investigated by studying
the dark and illumination (J-V) characterization of Au/FMN/p-Si/Al
heterojunction. The transport mechanism of the electronic charges are
determined for the heterojunction in the forward and reverse directions
in Au/FMN/p-Si/Al heterojunction. Results showed that the RR was
about 2.9 for room temperature. The determined values of Rs and Rsh
are found to be 0.48 KΩ and 4.85 KΩ, respectively. At low forward
voltages the transport mechanism is tunneling mechanism and at high
voltage is space-charge-limited conduction (SCLC) mechanism. In the
low voltage range, the current is due to thermally generated carriers,
while in the higher voltage range a bulk limited conduction process is
the dominated mechanism. The junction shows a photovoltaic behavior
with a maximum open-circuit voltage, 𝑉𝑜𝑐, of 0.19 V and a short-circuit
current density, 𝐽𝑠𝑐, of 102.7 mA/m2.
Finally the thesis represent an experimental study of XRD pattern
of 2-chloro-5-(2,5-dimethoxy-benzylidene)-1,3-diethyl-dihydropyrimidine-
4,6(1H,5H)-dione, a combined experimental and
computational study for the molecular structure and vibra frequencies of the investigated compound. The equilibrium geometries,
harmonic vibrational frequencies, thermo-chemical parameters, total
dipole moment and HOMO-LUMO energies are calculated by
DFT/B3LYP utilizing 6-31G and 6-31lG basis sets. Our calculated
results have showed that 2-chloro-5-(2,5-dimethoxy-benzylidene)-1,3-
diethyl-dihydro-pyrimidine-4,6(1H,5H)-dione possesses a dipole
moment of 4.9 Debye and HOMO-LUMO energy gap of 3 eV.
We also represent the optical properties of 2-chloro-5-(2,5-
dimethoxy-benzylidene)-1,3-diethyl-dihydro-pyrimidine-4,6(1H,5H)-
dione: transmittance (T), reflectance (R), optical constants (n,k),
absorption coefficient (𝛼), molar extinction coefficient (𝜀𝑚𝑜𝑙𝑎𝑟),
oscillator strength (𝑓), electric dipole strength (𝑞2), energy gap (𝐸𝑔),
single oscillator energy (𝐸0), dispersion energy (𝐸𝑑) and dielectric
constant (𝜀𝐿). X-ray diffraction results indicate that powder of the
investigated compound has a polycrystalline nature with a monoclinic
structure. Effect of annealing on the optical properties was investigated.
The values of the energy band gap are calculated using an optical
method. The type of the optical transition responsible for the optical
absorption is direct allowed transition. The refractive index showed an
anomalous dispersion in the absorption region as well as a normal one
in the transparent region. The dispersion parameters of 2-chloro-5-(2,5-
dimethoxy-benzylidene)-1,3-diethyl-dihydro-pyrimidine-4,6(1H,5H)-
dione films are determined and they are affected by annealing effect